Late last Thursday night, Wellesley High School history teacher and Watertown resident Stephanie Cacace was getting ready for bed when she heard a massive explosion.

Just a few minutes earlier, Cacace, 31, had been asleep on the couch when her husband woke her to tell her that a Massachusetts Institute of Technology campus police officer had been shot and someone had carjacked a vehicle on nearby Memorial Drive, the Wellesley Townsman reported

Cacace said her husband was convinced the incidents were related to the April 15 Boston Marathon bombing, because things like that just didn’t happen in Cambridge, or Watertown, for that matter.

While preparing to go to bed, her husband kept his attention glued to the police scanner application on his cell phone.

"He was just listening to the events unfolding in Cambridge," she said.

At the time, the Dexter Avenue resident had no idea what the next 22 hours would hold for her and her neighbors.

After noise from the explosions ripped through her neighborhood, Cacace said her husband "looked at me and he said the scanner was saying [the bombing suspects] are on Dexter Avenue and they have explosives."

The two grabbed their sleeping 2-year-old son and rushed into their home’s finished basement bathroom, keeping the police scanner nearby.

"While we were running downstairs to the bathroom we heard rapid gunfire…a constant stream of bullets. We went into the bathroom downstairs and listened to the police scanner app describe the events as they were unfolding."

"We heard them say they had captured the first suspect [Cambridge resident Tamerlan Tsarnaev, 26]…and they were concerned there were unexploded bombs in the area, and they were going to be investigating. We heard them try to pursue the second brother [Cambridge resident Dzhokhar Tsarnaev, 19]; they were pursuing several leads in the community…in different sections of Watertown." Cacace later learned that Tamerlan, known the world over as suspect one, had been killed during a shootout with police.

The early hours of Friday morning proved to be terrifying for Cacace.

"Truthfully it was absolutely surreal," she said. "The moment there were explosives, you can’t really comprehend there is somebody who has a bomb on your street, and you don’t know really where they are…that was probably the most frightening part at first."

Around 3 a.m., the couple decided to the leave the windowless basement bathroom they had been taking shelter in since midnight

"My husband looked out the basement windows and could see police all up and down the street…it was like we had a personal security force or something."

Shortly after, Cacace said she received a robocall from the town informing residents that Watertown was an active crime scene and to stay inside their homes.

When daylight arrived, Cacace said she and her husband felt it was safe to finally leave the basement. They spent the rest of the day following media reports – much like the rest of the greater Boston area and beyond – and staying in a back room just to be safe.

"Our house was searched twice by SWAT teams," Cacace said. "It was like being in a war zone. It was like images of Iraq or the Gaza Strip."

Outside her home, Cacace said she saw police in riot gear with automatic weapons, police officers in standard uniforms with pistols, FBI agents and ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives) agents patrolling the area, "looking into different homes, at times seeming more relaxed and at other times more tense," throughout the day.

But she wasn’t upset when authorities searched her residence.

"They only searched our first floor (Cacace lives in a three-story home), basement and garage," she said. "They were very friendly."

Authorities asked if she needed anything, if they were OK and if they wanted police to search any areas they had not previously covered.

"They didn’t storm into anyone’s home and point guns at anyone. It was very professional and amicable."

For Cacace, the most terrifying point was when the lockdown -- which had been in effect in Watertown, Boston, Cambridge, Belmont and Newton since early Friday morning -- was lifted at 6 p.m., but the second suspect had still not been caught.

"That was truly the most frightening moment," she said.

Since residents were no longer required to stay in their homes, Cacace and her husband decided to get out of the city and stay with her in-laws in Connecticut.

"As we were packing up we heard the second round of gunshots," she said. At first, she was panicked, but panic soon faded into relief.

"This is good, it means it’s going to end…at least it’s not going to be in my neighborhood anymore," she said.

Cacace returned to the basement with her family, and after listening to the police scanner, learned the suspect had been located hiding in a boat about a mile from her home.

"Once we found out he was surrounded, we came back upstairs and watched the final capture on the TV."

Nineteen-year-old Dzhokhar Tsarnaev was taken into custody, alive but in serious medical condition, around 9 p.m., ending a day of "being in heightened anxiety" for Cacace and her husband.

Cacace said she was lucky her son was too young to understand what had just occurred.

"Fortunately he never clued into what was happening. I do know there are children in our neighborhood who are traumatized."

And Cacace did not escape the day emotionally unscathed either.

"It’s been hard. The hardest part has been that, coming to work here in Wellesley, nobody really understands what you went through, and that’s not their fault."

Even though she wasn’t injured, her home wasn’t destroyed and every image of the day was relayed through either a phone or a TV screen, Cacace said that "nonetheless, the fear is real and the trauma and anxiety is real. It’s hard for people to understand that."

But Cacace has found some solace talking about the events with students in her classes at the high school this week.

"In some ways they are much more honest and they don’t have this script of ‘I’m sorry for you, that must have been scary,’ like adults do," she said.

"The genuineness of high-schoolers I’ve found very comforting; that was an important part of learning to be able to speak about it and move forward."

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